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        //    ES5
        let age  = 18;
        console.log("age outer ",age);
        
        function sayAge(){
            
            console.log("age  inner ",age);
            
            let age = 15;  //无法检查语法错误
          
        }

        sayAge()


        //常亮
        const pi = 3.14;


        // pi = 300.14 
        // console.log("pi",pi);

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